The proposed study will comprehensively document the injection initiation experiences and early injection careers of young injectors (age 16-25) in New York City, with an emphasis on the impact of pedagogy on the development of injection skills and the acquisition of these skills over time. A large sample (n=600) of cross-sectional interviews, as well as bimonthly interviews with a cohort (n=150) of new injectors will be supplemented with direct ethnographic observations (n=200) of injection events involving young injectors. Data from these interviews and observations will be used to characterize the injection initiation experiences of young injectors, describe the process by which new injectors learn the behavioral practices necessary to prepare and inject drugs, and determine predictors of safer injection behaviors that may prevent the transmission of HIV, HBV, and HCV. A focus on help-seeking skills will inform the development of recommendations for competencies-based interventions aimed at preventing seroconversion among new injectors.